The invention relates to an aircraft air conditioning system and a method for operating an aircraft air conditioning system.
In commercial aircraft, so-called air-supported air conditioning systems such as are described, for example, in DE 10 2008 053 320 B4 and U.S. Pat. No. 8,333,078 B2 or EP 2 651 763 A2 and US 2013/269374 A1 are normally used at present for air conditioning the aircraft cabin. An aircraft air conditioning system is used for adjusting and maintaining a desired pressure, a desired temperature and a desired air humidity in an aircraft cabin. Furthermore, the aircraft air conditioning system supplies adequate fresh air to the aircraft cabin in order to ensure that a prescribed minimum amount of fresh air is present in the aircraft cabin.
Air-supported aircraft air conditioning systems normally comprise an air conditioning unit, to which compressed process air is supplied from the engines of the aircraft, a separate compressor or an auxiliary engine (APU, Auxiliary Power Unit). In flight mode of the aircraft, engine bleed air is predominantly used to supply the air conditioning unit of the aircraft air conditioning system with compressed process air. In ground operation of the aircraft, on the other hand, compressed process air is normally supplied to the air conditioning unit of the aircraft air conditioning system from the auxiliary power unit or an air production unit outside the aircraft. In the air conditioning unit the process air is cooled and expanded upon flowing through at least one heat exchanger unit and various compression and expansion units. Cooled process air emerging from the air conditioning unit is finally conducted into a mixing chamber and mixed there with recirculation air taken away from an aircraft area to be air conditioned. The mixed air from the mixing chamber is conducted via corresponding mixed air lines into the aircraft area to be air conditioned, which can be in the form of a passenger cabin, a cockpit, a cargo hold, a crew rest room or similar.
DE 10 2010 034 830 A1 and WO 2012/022758 A1 describe an aircraft air conditioning system in which compressed process air, which is taken from an engine of the aircraft, is cooled by the transfer of heat to a coolant flowing through a cooling circuit. A turbine, which serves to expand the compressed process air before it is supplied to an aircraft cabin, is used to drive a compressor arranged in the cooling circuit.
An aircraft air conditioning system is known from EP 2 821 346 A1 and US 2015/013355 A1 that comprises an ambient air supply line adapted to be flown through with ambient air. An ambient air cooling apparatus, which is connected to the ambient air supply line, is configured to cool the ambient air flowing through the ambient air supply line. The aircraft air conditioning system further comprises an ambient air discharge line, which is connected to the ambient air cooling apparatus and connectable to an aircraft cabin, and a supply line for compressed bleed air, which is adapted to be flown through with compressed air. A cooling apparatus for compressed air is connected to the supply line for compressed bleed air and is configured to cool the compressed air that flows through the supply line for compressed bleed air. A discharge line for compressed air is connected to the cooling apparatus for compressed air and is connectable to the aircraft cabin. A refrigerating apparatus comprises a refrigerant circuit which is adapted to be flown through with a two-phase refrigerant and is configured to convert the two-phase refrigerant on flowing through the refrigerant circuit from the liquid state of aggregation to the gaseous state of aggregation and then from the gaseous state of aggregation back to the liquid state of aggregation again, wherein the refrigerant circuit of the refrigerating apparatus is configured to supply cooling energy to the ambient air cooling apparatus and the cooling apparatus for compressed air.